make test_support's captured_output a bit more robust when exceptions happen

git-svn-id: http://svn.python.org/projects/python/trunk@62604 6015fed2-1504-0410-9fe1-9d1591cc4771

Author: benjamin.peterson

Lib/test/test_support.py

@@ -482,8 +482,10 @@ def captured_output(stream_name):
     import StringIO
     orig_stdout = getattr(sys, stream_name)
     setattr(sys, stream_name, StringIO.StringIO())
-    yield getattr(sys, stream_name)
-    setattr(sys, stream_name, orig_stdout)
+    try:
+        yield getattr(sys, stream_name)
+    finally:
+        setattr(sys, stream_name, orig_stdout)
 
 def captured_stdout():
     return captured_output("stdout")